NCERT Class XI Mathematics - Trigonometric Functions - Solutions
© examsnet.com
Question : 47
Total: 61
cos 4x = cos 2x
Solution:
We have, cos 4x = cos 2x ⇒ cos4x – cos2x = 0
⇒ - 2 sin(
) (
)
⇒ (sin 3x) (sin x) = 0 ⇒ either sin 3x = 0 or, sin x = 0
⇒
}
Since if sin x = 0 , then x = nπ , n ∊ Z
Hence x = nπ or
⇒ - 2 sin
⇒ (sin 3x) (sin x) = 0 ⇒ either sin 3x = 0 or, sin x = 0
⇒
Since if sin x = 0 , then x = nπ , n ∊ Z
Hence x = nπ or
© examsnet.com
Go to Question: